Saturday, May 7, 2016

RCGF 10cc Muffler Adaptation

In order to get the cowl on the pipe on the muffler had to be trimmed about 1-2 cm. This short stack sprays the airframe with oil... I don't think it affects performance much.

On the 30cc DLE I used rc car muffler couplers as extensions and they work awesome. I found a couple of options for the Spitfire and tried them out this morning.

This is the full car extension, comes with a short coupler and the extension. The bent pipe is soft silicone, but is about 6 mm or so ID. The muffler pipe on the engine is 10mm ID. Thats a 40% loss in diameter, and Poiseulle adroitly predicts a significant increase in resistance to flow (1/r4). I expected some significant back pressure and figured on some rpm loss.

This lasted 3 min. The solder bead I had on the muffler melted off as I expected it might, and the engine threw the extension and coupler off. She immediately gained the almost 500-600 rpms she lost due to back pressure. So much for that one...

So I went with just the longer coupler, and she runs fine. It gives me that 1-2 cm back, but I suspect there will still be some oilage. RPM performance is maxed, around 8200 rpm at full.

I hope to maiden her out in Hudson next week. Need a good clear, calm day.

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Men fear thought as they fear nothing else on earth -- more than ruin -- more even than death.... Thought is subversive and revolutionary, destructive and terrible, thought is merciless to privilege, established institutions, and comfortable habit. Thought looks into the pit of hell and is not afraid. Thought is great and swift and free, the light of the world, and the chief glory of man. ~ Bertrand Russell